Page 18 - macneill1947

15.

A major fault strikes northwesterly across tl~ Humphreys

Station area. North of this fault, and beneath a greenish-

brown marine formation called Pico, appear wedges of creamy

buff to rusty colored pebble conglomerate, sandstone and silt-

stone. Limy concretions and cong.Jooeratic beds are locally rich

in fossils. ·rhese wedges lie at an angular discordance of a

few degrees from the overlying brown formations. Descriptively

they resemble the lower section of the Pico as described by Kew

(op. cit. p. 73J from west of Towsley Canyon.

Although certain faunal species collected here indicate

an affinity to the conventional Lower Pliocene, two types have

never been recorded from strata younger than Upper Miocene.

This fact, in conjunction with the angular relations, is the

reason for their being included here with the ''Modelo". Some

of these wedges have the characteristics of reefs. From one of

them, the invertebrate and vertebrate fossils listed below were

collected (see Figure II). High angular discordances charac-

terize the contact between these wedges and the underlying Mint

Canyon formation.

Two small areas, just east of U.S. Highway 6, are

questionably shown as "Modelo" on the accompanying map. They

are composed of brownish and greenish-gray thin bedded shales

and siltstone with sandy members. Although no fossils were

found in them, their stratigraphic position adjacent to the

downthrown side of the fault, their more compact nature, (as
opposed to the .t'ico shales} and their attitudes, suggest a

correlation with the "Modelo". Possibly they represent a

slightly more seaward faoies.